The manufacture of H.sub.2 S from the reaction of natural gas (i.e., primarily methane) and sulfur is known The reaction products (H.sub.2 S, CS.sub.2 and unreacted sulfur) are formed when methane and excess sulfur are converted at elevated temperature according to the reaction of equation (I): ##STR1## A one-step process for manufacturing H.sub.2 S from natural gas, sulfur and steam is also known. The components are all combined to form H.sub.2 S and carbon dioxide (CO.sub.2) according to the reaction of equation (II): ##STR2## Major disadvantages of the one-step process of equation (II) include: (1) The subsequent removal of unreacted sulfur from the other reaction co-products is often difficult. Removal of unreacted sulfur by solidification and remelting, in downstream condensers, is often incomplete, resulting in equipment plugging.
(2) The process fails to provide a means for condensing and recycling excess water. As a result, the excess water is limited to the amount of water vapor that leaves with the vapor reaction products (usually about a 25 wt. % excess). This condition produces fairly high quantities of COS (e.g., 0.58 wt. %) in the H.sub.2 S/CO.sub.2 reaction product stream. PA1 (a) combining CS.sub.2 or a H.sub.2 S/CS.sub.2 mixture with water to form a feed mixture; PA1 (b) converting a substantial portion of the CS.sub.2 in the mixture by hydrolysis to a hydrolysis reaction vapor product comprising H.sub.2 S, CO.sub.2, sulfur and unconverted CS.sub.2 ; and PA1 (c) cooling the hydrolysis reaction vapor product to form a H.sub.2 S/CO.sub.2 vapor phase and a sour water condensate phase; and PA1 (d) separating the H.sub.2 S/CO.sub.2 vapor phase from the sour water condensate phase. PA1 (a) reacting natural gas with excess sulfur at elevated temperature to form a H.sub.2 S/CS.sub.2 reaction product comprising H.sub.2 S, CS.sub.2 and unreacted sulfur; PA1 (b) removing the unreacted sulfur from the H.sub.2 S/CS.sub.2 reaction product to form a substantially desulfurized H.sub.2 S/CS.sub.2 mixture; PA1 (c) combining the substantially desulfurized H.sub.2 S/CS.sub.2 mixture with water to form a feed mixture; PA1 (d) converting a substantial portion of the CS.sub.2 in the feed mixture by hydrolysis to a hydrolysis reaction vapor product comprising H.sub.2 S, CO.sub.2, sulfur and unconverted CS.sub.2 ; PA1 (e) cooling the hydrolysis reaction vapor product to form a H.sub.2 S/CO.sub.2 vapor phase and a sour water condensate phase; and PA1 (f) separating the H.sub.2 S/CO.sub.2 vapor phase from the sour water condensate phase. PA1 mixing the sour water condensate with additional CS.sub.2 to form a sour water phase and a CS.sub.2 phase containing dissolved sulfur; PA1 separating the sour water phase from the CS.sub.2 phase; and PA1 recycling the sour water phase to the H.sub.2 S/CS.sub.2 mixture in step (a), above. PA1 (i) cooling the hydrolysis reaction vapor product in a first cooling step to a temperature greater than the solidification point of sulfur; and PA1 (ii) cooling the vapor product in a second cooling step to a temperature no lower than about 30.degree. C. to form a H.sub.2 S/CO.sub.2 vapor phase and sour water condensate phase.
(3) The process increases equipment corrosion due to the presence of water vapor at elevated temperature (i.e., 1150.degree. F./621.degree. C.). The process does not provide a way of reducing the reaction temperature to a value where corrosion is minimized (i.e., 700.degree. F./37l.degree. C.).
Once the reaction of equation (I) takes place, H.sub.2 S may be recovered from its gaseous mixture with CS.sub.2 by converting CS.sub.2 to additional H.sub.2 S in a fixed bed hydrolysis reactor. It is possible by hydrolysis with steam to convert almost all of the CS.sub.2 (to a total concentration of up to 6 volume percent CS.sub.2) found in the gaseous mixture consisting mostly of H.sub.2 S. The conversion takes place according to the reaction of equation (III): ##STR3## A catalyst is often used in the fixed bed hydrolysis reactor to catalyze the above reaction. The hydrolysis reaction is highly exothermic and takes place in the absence of oxygen. Reactor outlet temperatures well in excess of 700.degree. F./371.degree. C. are possible. However, in situations where the CS.sub.2 concentration is often in excess of 6 volume percent, the above-identified hydrolysis process is not workable since large excesses of water are required to control the hydrolysis reaction outlet temperature. Moreover, the small amounts of sulfur which are formed in CS.sub.2 hydrolysis must be subsequently removed in order to avoid equipment plugging.
Clearly what is needed is a process capable of converting CS.sub.2 to additional H.sub.2 S in a H.sub.2 S/CS.sub.2 mixture which does not have the disadvantages inherent in the prior art. The process should permit substantially complete conversion of CS.sub.2 to H.sub.2 S under conditions which minimize COS formation, energy expenditures, and equipment plugging. Conversion should take place where high concentrations of CS.sub.2 are present within the H.sub.2 S (&gt;&gt;6 vol.% CS.sub.2 ). In particular, conversion of CS.sub.2 to H.sub.2 S by hydrolysis should be conducted under conditions where a relatively low temperature (i.e., 700.degree. F./371.degree. C.) is maintained at the outlet of the hydrolysis reactor so that the reactor also converts COS to additional H.sub.2 S and so that equipment corrosion is minimized.
Other objects and advantages of the present invention will become apparent to those skilled in the art with reference to the attached drawing and the description of the invention which hereinafter follows.